This invention relates to a dental implant comprising an implant body which can be anchored in a jawbone and a superstructure portion which can be inserted at least partially in a recess arranged on the coronal end of the implant body and which can be fastened in the implant body by a holding screw, wherein the recess comprises at least one first contact surface which contacts an associated second contact surface on the superstructure in order to secure the parts against relative rotation.
Schulte et al., U.S. Pat. No. 5,199,873 discloses a dental implant which has an implant body that can be anchored in the jawbone. At the coronal end, the implant body has a recess in which a superstructure portion can be partially inserted and can be fastened by means of a holding screw. In order to affix the superstructure portion so that it cannot rotate relative to the implant body, at least one contact surface is provided in the recess, against which an associated contact surface of the superstructure portion rests in a form-keyed manner. These contact surfaces are advantageously designed in the shape of a hexagon and produce a rotation stop while being easy to handle. However, two-phase dental implants of this type exhibit rotational play at the connection between the superstructure portion and the implant body, which play leads to inaccurate positioning. Furthermore, such relative movements may lead to loosening of the holding screw as well as to frictional corrosion in the gap area between the superstructure and the implant body. For manufacturing reasons, a fit between the superstructure portion and the implant body that is free from play cannot be achieved, because otherwise it would be impossible to insert the superstructure portion in the implant body. It has been found in practice that, even if the superstructure portion and the implant body are manufactured with a high precision form-keyed hexagon connection, a play of from 2 to 3 degrees of angle about the longitudinal axis may occur. In addition, in dental implants of this type, a defined axial positioning of the superstructure portion with respect to the implant body is essential. Thus, conical fittings, which are known not to enable precise axial positioning, cannot be used to establish a play-free connection between the superstructure portion and the implant body.
Furthermore, Reuther et al, Swiss Patent No. CH 642,838 discloses a dental implant which comprises an implant body which can be inserted into the jawbone, a plastic bearing and a superstructure portion or implant carrier. The plastic bearing is screwed into a conical bore of the implant body and contains a coaxial internal bore with a thread. A threaded pin on the superstructure portion is screwed into this internal bore. Plastic deformation of the plastic bearing results in a pseudo-conical clamping, so that a tight connection can be established by screwing the parts together. However, there is nothing to prevent relative rotation between the superstructure portion, on the one hand, and the implant body, on the other hand.
Perisse, French Patent No. FR 2,663,836 discloses a dental implant having a hollow, substantially cylindrical implant body. The apical end of the superstructure portion, which can be inserted into the implant body, is formed with a slot and contains an internal through-bore which is filled with balls or the like and which converges at the apical end so that the balls cannot pass through the slot. Pressure can be applied to the balls by means of a screw which is arranged in the through bore at the coronal end of the superstructure portion, so that the superstructure portion is spread apart at the apical end and is pressed in the recess of the implant body. Thus, the superstructure portion is affixed to the implant body without a holding screw screwed into the implant body and without any means for preventing relative rotation.
Caracciolo, U.S. Pat. No. 4,S88,381 discloses an implant comprising a tube-shaped implant body. At the apical end, the implant body is provided with slots, and the internal bore is designed in a conically tapering manner. When the superstructure portion is screwed in, the implant body is spread at the apical end in order to anchor the implant. In this case, there is no fixing due to compression, like that achieved when using a holding screw. Also, it is not possible to precisely position the superstructure portion in the implant body in this manner.
Fath, Published German Patent Application No. DE 4,000,112 discloses a dental implant with an implant body which again has a slotted design on its apical end and which is provided with a central recess. A screw can be screwed into this recess, whereby the tip of the screw spreads open the end of the implant body as it is screwed in and anchors the implant in the bone. This implant does not provide any advantageous teachings with regard to fastening the superstructure to the implant body or to fixing their positions and securing them against relative rotation.